1.Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a multi-domain LCD device in which a liquid crystal is diversely driven by an auxiliary electrode.
In general, an LCD device is provided with lower and upper substrates facing each other at a predetermined distance, and a liquid crystal layer formed between the lower and upper substrates.
There are several types of LCD devices including a vertical alignment mode LCD device, which uses a negative liquid crystal of a negative dielectric anisotropy. In a state where voltage is not applied, a longitudinal direction of a liquid crystal molecule is arranged perpendicular to an alignment layer. When the voltage is applied, the longitudinal direction of the liquid crystal molecule is twisted to the alignment layer due to an electric field. In this respect, transmissivity of light is controlled in the LCD device, thereby displaying an image.
In order to obtain a wide viewing angle, the vertical alignment mode LCD device includes a side electrode and a rib/slit on the substrate. That is, the liquid crystal molecules are arranged at a desired direction by deteriorating the electric field applied to the liquid crystal layer (for example, a patterned vertical alignment (PVA) mode and a multi-domain vertical alignment (MVA) mode). The explanation for the above modes follows with reference to the accompanying drawings.
FIG. 1A is a sectional view showing a unit pixel of a related art LCD device in which a liquid crystal is driven by a auxiliary electrode.
The related art LCD device includes first and second substrates (not shown), a plurality of gate and data lines (not shown), a thin film transistor (not shown), a pixel electrode 1, a passivation film 3, a side electrode 5, a black matrix film (not shown), a color filter film 7, a common electrode 9 and a liquid crystal layer (not shown).
The plurality of gate lines are formed on the substrate to cross the plurality of data lines, thereby defining a plurality of pixel regions. Then, the thin film transistor (TFT) formed at the pixel region includes a gate electrode, a gate insulating layer, a semiconductor layer, an ohmic contact layer and source/drain electrodes. The pixel electrode 1 is formed at the pixel region to connect to the TFT, and the passivation layer 3 is formed on an entire surface of the first substrate including the pixel electrode 1. Next, the side electrode 5 is formed on the passivation layer 3 to overlap with the pixel electrode 1, and the black matrix film is formed on the second substrate to prevent light from leaking in the gate line, the data line and the TFT. Then, a color filter film 7 is formed on the black matrix film, and the common electrode having an open region 8 is formed on the color filter film. The liquid crystal layer is formed between the first and second substrates.
In the related art LCD device having the aforementioned structure, the electric field is applied to the liquid crystal layer. At this time, the electric field is deteriorated by function of the open region 8 within the common electrode 9 and the side electrode 5 around the pixel electrode 1.
Accordingly, the liquid crystal molecules are arranged in the desired direction by dielectric energy of the fringe electric field, so that the liquid crystal molecules of the unit pixel are driven in various directions, thereby obtaining multi-domain effect.
However, in order to form the side electrode 5 on the pixel electrode, it is additionally required to form the passivation film 3, to pattern the side electrode 5, and to form the open region 8 in the common electrode 9 in the related art LCD device.
Also, if the width of the open region 8 is narrow, a lot of time is spent to arrange the liquid crystal molecules stably since the electric field for dividing the pixel region into a plurality of domains is slightly deteriorated.
Accordingly, an LCD device has been proposed in Korean Application P1999-7633 filed on Apr. 9, 1999 in which the auxiliary electrode is formed on the same layer with the gate line to simplify the manufacturing process steps, and a dielectric structure is formed on the common electrode without forming the open region on the common electrode.
FIG. 1B is a sectional view showing an LCD device of the Korean Application P1999-7633 (U.S. application Ser. No. 09/327,283).
Referring to FIG. 1B, the LCD device includes first and second substrates (not shown), a plurality of gate and data lines (not shown), a pixel electrode 1, a common side electrode 5, a black matrix film (not shown), a common electrode 9, a dielectric structure 6 and a liquid crystal layer (not shown).
The plurality of gate lines are formed on the first substrate to cross the plurality of data lines, thereby defining a plurality of pixel regions. Then, the pixel electrode 1 having an electric field induction window 2 is formed in the pixel region, and the common side electrode 5 is formed on the same layer with the gate line, and is overlapped with an edge of the pixel electrode 1. After that, the passivation film 4 is formed beneath the pixel electrode 1, and the black matrix film (not shown) is formed on the second substrate. The color filter film 7 is formed on the black matrix film, and the common electrode 9 is formed on the color filter film 7. Next, the dielectric structure 6 is formed on the common electrode, and the liquid crystal layer (not shown) is formed between the first and second substrates.
However, in the aforementioned LCD device, the electric field is deteriorated and becomes unstable in regions of the dielectric structure 6 and the electric field induction window 2, so that it is difficult to obtain a stable texture, and a residual image generates on the display panel.